Hot working tools

Rolls of plate mills, mentioned in section 9.4.1.1, can attain, during hot lamination, working speeds of more than 500 m/s. In a particularly corrosive medium, cobalt can be replaced by a Ni/Co/Cr (15% to 20%) binder. 

Without sintered hard metals, the synthesis of diamond and CBN, and the sintering of PCD and PCBN would not have been possible. High temperature (500°C on the carbide wall, 1,500°C at the core of the chamber) and high pressure (12 to 15 GPa) chambers are made up of a die (10% to 12% Co 0wc = 2-3 pm) and punches (6% Co) inbinaiy grades WC-Co. 

In applications requiring swing joints of single form, standard size and without any requirements of toughness, silicon carbide can replace sintered hard metals. 

As we have seen in this chapter, on various occasions, the excellent combination of properties on account of their composite nature explains the almost unequalled success of sintered hard metals in a large number of fields of technology. They are still growing in importance despite having been around for 75 years. The appearance of new materials (ceramics, superhard materials) has not dampened the momentum of fundamental and applied research on sintered hard metals. The accent is now placed on technoeconomic gains and the increase in duration of the life of tools, combined with effective methods of recychng. 

1) Percussive mining tools Mining and civil engineering tools Masonry and stone cutting tools 

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Group H covers hot work tool steels, which retain strength, toughness and resistance to softening at elevated temperatures. Group H steels are very strong and have important structural applications, such as rolls and fasteners (e.g., HI 1 and HI3). 

Hot work tool steels are used in most shearing applications that take place at hot rolling temperatures (1600-2000°F for steel). Good knife cooling practices are important to minimize heat checking and assure proper knife performance. 

Superalloys are much more costly than tool steels, but these grades are applicable when a significantly longer knife life is desired. These high-performance alloys are not as susceptible to thermal cracking and maintain their strength at elevated temperatures, therefore knife cooling is not as critical compared to hot work tool steels. 

Hot-work tool steel DIN 1.2343 steel (hardness approximately 44 on the Rockwell C Hardness Scale (HRC), thermal conductivity around 25 W/mK) for nozzle casings and bodies ... 

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